xhci: refactor transfer event errors and completion codes

Parse the transfer event first, and remove duplicate debugging
code.

Reorder completion codes according to endpoint state.

No functional changes

We are not handling some transfer events correcly and need to
clean up this before fixing it

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>